Production of hollow components for rolling element bearings by diffusion welding

ABSTRACT

A hollow rolling element for a bearing is fabricated by diffusion welding hollow shells together.

United States Patent [1 1 Moore m1 3,748,722 July 31, 1973 1 PRODUCTIONOF HOLLOW COMPONENTS FOR ROLLING ELEMENT BEARINGS BY DIFFUSION WELDING[75] lnventor:

[73] Assignee: The United States of America as represented by theAdministrator of the National Aeronautics and Space Administration,Washington, DC.

[22] Filed: Nov. 9, 1971 [21] Appl. No.: 196,970

Thomas J. Moore, Berea, Ohio [52] U.S. Cl 29/487, 29/494, 29/497.5,-

[51] Int. Cl B231: 31/02 [58] Field of Search 29/498, 493, 494,29/497.5, 487

[56] References Cited UNITED STATES PATENTS 1,316,384 9/1919 Murray, Jr.et al...., 29/498 UX OTHER PUBLICATIONS Garrett et al., BroadApplications of Diffusion Bonding, NASA CR-409, March, 1966, pp. 19-25,32-36, 80-84 and 138-140. Tech. Library.

Primary Examiner-J. Spencer Overhoiser m"? nema- 19m Sh w Attorney-N. T.Musial, John R. Manning et al.

[57] ABSTRACT A hollow rolling element for a bearing is fabricated bydiffusion welding hollow shells together.

3 Claims, 3 Drawing Figures PATENTEDJULB? 197s SHEET 2 BF 2 LA MATINGSURFACES DEGREASE ASSEMBLE PREFORMED COMPONENTS APPLY DEAD-WEIGHTLOADING TO AS SEM BLED COMPONENTS HEAT ASSEMBLED COMPONENTS TN VACUUMFURNACE REMOVE FROM FURNACE FIG.

INVENTOR THOMAS J. MOORE PRODUCTION OF HOLLOW COMPONENTS FOR ROLLINGELEMENT BEARINGS BY DIFFUSION WELDING ORIGIN OF THE INVENTION Theinvention described herein was made by an employee of the United StatesGovernment and may be manufactured and used by or for the Government forgovernmental purposes without the payment of any royalties thereon ortherfor.

BACKGROUND OF THE INVENTION This invention is concerned with hollow highstrength rolling elements for bearings. The invention is particularlydirected to an improved method of fabricating hollow balls and rollersfrom preformed components.

I-Iollow rolling elements, such as balls and rollers, are used inbearings to reduce weight. Less energy is required for aceleration anddeceleration with hollow rolling elements because of their lowerinertia.

Electron beam welding has been used to fusion weld preformed halves ofhollow rolling elements. Areas of high stresses resultedfrom thiswelding process because of excess weld metal or undercut at the root ofthe weld. When electron beam welded hollow rolling elements are placedin service cracking tends to start near the root of the weld causingfailure of the bearing.

SUMMARY OF THE INVENTION These problems have been solved by fabricatinghollow bearing elements by welding in accordance with the presentinvention. The hollow shell halves are joined by preparing the fayingsurfaces of the rolling element components and then diffusion welding.No macrodeformation is involved, and no foreign material is introducedat the joint.

OBJECTS OF THE INVENTION It is, therefore, an object of the presentinvention to provide an improved welding method for fabricating hollowrolling elements for bearings.

A further object of the invention is to provide an improved hollowrolling element for a bearing.

These and other objects of the invention will be apparent from thespecification which follows and from the drawing wherein like numeralsare used throughout to identify like parts.

DESCRIPTION OF THE DRAWING FIG. 1 is a vertical section view ofapparatus for joining rolling elements in accordance with the presentinvention;

FIG. 2 is an enlarged sectional view taken along the line 2--2 in FIG.1; and

FIG. 3 is a flow sheet illustrating diagrammatically the process formaking hollow rolling elements in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawingthere is shown in FIG. 1 a hollow rolling element 10 that is fabricatedin accordance with the present invention. The rolling element 10 may beeither a ball or a roller and is made by joining two prefonnedcomponents 12 and 14 shown in both FIGS. 1 and 2. The components 12 and14 are in the form of half shells which are either hemispherical inshape for balls or hemicylindrical in shape for rollers. The preformedcomponent 12 has a mating or faying surface 16 extending about itsperiphery. The preformed component 14 has a similar surface 18 extendingabout its periphery. The faying surfaces 16 and 18 are lapped to ensureflatness for optimum mating contact.

Referring to FIGS. 1 and 3 the preformed components 12 and 14 areassembled by placing the surface 16 in contact with the surface 18. Thepreformed components are assembled in the aforementioned manner byplacing the two half shells l2 and 14 into a contoured assembly jig 20shown in FIG. 1. The jig 20 is of a suitable material, such ashigh-purity alumina that does not react with the rolling element. Thejig 20 includes a base member 22 having a suitable opening for receivinga slidable member 24. The base 22 has a contoured surface 26 which mateswith the half shell 14.

The slidable member 24 has a similarly contoured surface 28 which mateswith the half shell 12 as shown in FIG. 1.

The assembled components and the jig 20 are placed in a vacuum chamber30 as shown in FIG. 1. The vacuum chamber 30 is enclosed in a suitableinsulated container 32 having heating coils 34. The vacuum chamber 30together with the chamber 32 comprise a vacuum furnace. A low weldingpressure is applied to the assembled components by a dead weight 36. Thevacuum chamber 30 is evacuated to about 2Xl0" to 4Xl0' torr. Theassembled preformed components are heated in vacuum to a temperaturebetween 1,900F and 2,150F.

After the components 12 and 14 have been raised to this high temperatureunder the vacuum condition the low welding pressure is maintained on theassembled components by the dead weight 36. A very low welding pressureof about 4 psi is all that is required to form a hollow rolling element.This pressure is maintained on the heated components 12 and 14 forbetween A to 4 hours to diffusion weld the .componentsat the fayingsurfaces 16 audit).

The aforementioned process was used to diffusion weld balls each havinga diameter of eleven-sixteenths inch and a thickness of one-sixteenthinch. After welding the components in accordance with the aforementionedprocess the 11/16 inch diameter balls were found to be spherical in theas-welded condition. No excess material or undercut was present at thewelded joints.

While the preferred embodiment of the invention has been disclosed anddescribed it will be apparent that various modifications may be madewithout departing from the spirit of the invention or the scope of thesubjoined claims. By way of example, it may be desirable to heat treatthe welded rolling element after welding. The aforementioned ll/l6 inchdiameter balls were treated by heating to a temperature of 2,225F for 6minutes and oil quenching. The balls were then heated nace to anelevated temperature between 1,900F and 2,150F while maintaining saiddead weight pressure for about one-half hour to about 4 hours todiffusion weld said members at said flat surfaces. 2. A method asclaimed in claim 1 wherein the substantially flat surfaces are formed bylapping.

3. A method as claimed in claim 1 including the step of heat treatingthe rolling element after difl'usion weldmg.

i i i i i

1. A method of fabricating a hollow rolling element for a bearing frompreformed half shell members having a thickness of about one-sixteenthinch comprising the steps of forming a substantially flat surface aboutthe periphery of each of said members, assembling said members into saidhollow rolling element configuration in a jig with said flat surfaces inmating contact, placing said assembled members and said jig in a vacuumfurnace, evacuating said furnace to a pressure between about 2 X 10 5and 4 X 10 5 torr, applying dead weight pressure of about 4 psi to saidassembled members, and heating said assembled members in said vacuumfurnace to an elevated temperature between 1,900*F and 2,150*F whilemaintaining said dead weight pressure for about one-half hour to about 4hours to diffusion weld said members at said flat surfaces.
 2. A methodas claimed in claim 1 wherein the substantIally flat surfaces are formedby lapping.
 3. A method as claimed in claim 1 including the step of heattreating the rolling element after diffusion welding.